The Accessory Optic System is a constant component of the visual system of all vertebrates. Until recently, little was known of its connections or functions. This is a request for continued support for anatomical and histochemical investigation of this system. Research supported by this grant over the past two years has resulted in many major discoveries about this system, including the unique afferentation of the accessory optic system from displaced ganglion cells of the retina, and the specific direct efferent projections of the accessory optic system upon a) the oculomoter complex, b) the vestibulocerebullum, c) the inferior olive, d) the nucleus inter-stitialis specifically involved in orienting and/or image stabilization. A series of histochemical and biochemical studies currently in progress are directed towards an attempt to identify a) the specific transmitter(s) of the displaced ganglion cells and of the post synaptic cells within the accessory optic nuclear complex; b) Subsequent projections of the accessory optic system and relationship to other afferents involved in control of coulomotor, vestibular, and neck motorneurons. Continuing ontogenetic study of this system indicates that the accessory optic system and displaced ganglion cells are the temporal forerunners of all retinal systems projecting upon the brain. Additional projects include investigation of a) other possible specific classes of retinal ganglion cells related to particular tasks, with particular emphasis directed towards an analysis of ganglion cells possibly involved in pupillary control; b) Light and EM localization of peptides within the horseradish peroxidase histochemistry, autoradiography for anterograde transport of radiolabeled amino acids, electron microscopy, immunohistochemistry, autoradiography for high affinity uptake studies, radioimmunoassay of peptides, radioassay for chlorine acetyl transferase, etc.